Corticosteroid drugs are often required for asthma therapy. The mechanism of action is unknown and a dose-response relationship has not been established. The beta adrenergic blockade theory suggests that bronchospasm in asthma may be related to beta agonists and increase beta adrenergic receptor concentration in lung tissue. The clinical pharmacology of corticosteroids will be studied by an analysis of corticosteroid pharmacokinetics and effect on beta receptors. Alterations in beta receptor concentration on polymorphonuclear leukocytes (PMN) will be investigated as an indicator of corticosteroid dose response in normal volunteers and patients with asthma. These methods will be used to study the corticosteroid drug interaction and "steroid-sparing" effect of troleandomycin in severe steroid-dependent asthmatics. An animal model will be developed to relate changes in receptor concentration on PMN's to that in lung tissue and to conduct studies on the role of the glucocorticoid receptor in the regulation of beta receptor activity. Since elimination rate may alter response to corticosteroids and children often eliminate drugs faster than adults, pharmacokinetics will be studied in children to initiate an evaluation of corticosteroid dosing regimens in this age group.